The use of inkjet printers for the production of paper proofs of digital photographic images is known, for example, from PCT Application WO 97/28003. One particular problem encountered in this context is that when a full-bleed paper proof is produced by printing over the sides of the recording medium, ink gets onto the transport substrate, for example a transport belt or transport roller. The ink consequently becomes smeared onto the backside of the next paper proof being printed, so that the printout becomes unusable. In addition, the deposits of ink residues can eventually result in paper transport malfunctions in the printer.
To regulate the lateral position of a material web, it is known from PCT Application WO 96/38370 that the lateral position of web edges is sensed, in the context of processing of continuous paper webs, by way of a CCD sensor, in which light beams reflected from a region on either side of the web edge strike a CCD line extending perpendicular to the travel direction of the material web. The voltage signals thereby produced, which are analogous to the illumination intensity, are displaced along the CCD line using a shift clock cycle; at the output, they are picked off individually and compared [in] at least one comparator to an adjustable threshold value. If deviations from a setpoint exist, a correction signal is generated that triggers, via an electronic control system, an actuating signal for regulating the lateral position of the material web.
Also known, from European Patent 0 570 167 A2, is a method for controlling the print density of an inkjet printer in which first a predefined printed line width is selected, the printing medium is positioned under the printing head, and then a line is printed. The width of the printed line is sensed by way of an optical sensor, and the difference between the predefined and printed widths is determined.
The known existing art cited above thus discloses only solutions for controlling or positioning printing media or recording media relative to a printing head. A digital printing method for the production of photo proofs that avoids the aforesaid problems and costs associated with print production is not known.
It is the object of the invention to describe a method for controlling printing nozzles of a full-line printing head in an inkjet printer with which printing beyond the edge of a printing medium can be prevented.